Polymeric plate bendable without thermal energy and methods of manufacture

ABSTRACT

An implantable plate for providing support to a bone of a subject when affixed thereto includes a polymeric body of a biocompatible polymer having a desired amount of polymer molecule orientation in a first direction so that the plate can be bent to conform with a contour of the bone of the subject. The polymeric body includes a top surface, a bottom surface, and at least one fastener portion. The fastener portion includes a recess and a fastener hold that is configured for receiving a fastener when affixed to the bone of the subject. A method of manufacturing the implantable plate includes: (1) injection molding a biocompatible polymeric composition into a polymeric body within an injection mold; (2) removing the polymeric body from the injection mold; and (3) forming at least one fastener hole within polymeric body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This United States Patent Application is a Continuation of U.S. patentapplication Ser. No. 11/146,454, filed Jun. 6, 2005, and entitled“POLYMERIC PLATE BENDABLE WITHOUT THERMAL ENERGY AND METHODS OFMANUFACTURE,” with Randolf Von Oepen and Alexander Tschakaloff asinventors, which claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 60/577,638, filed on Jun. 7, 2004, andentitled “POLYMERIC PLATE BENDABLE WITHOUT THERMAL ENERGY,” with RandolfVon Oepen and Alexander Tschakaloff as inventors, the entireties ofwhich are incorporated herein by reference. Additionally, this UnitedStates Patent Application cross-references other United States PatentApplications filed simultaneously herewith on Jun. 6, 2005, namely U.S.patent application Ser. No. 11/145,692, entitled “FASTENER HAVING TORQUEOPTIMIZED HEAD” with Randolf Von Oepen as inventor, and U.S. patentapplication Ser. No. 11/146,433, entitled “SELF FORESHORTENING FASTENER”with Randolf Von Oepen as inventor. The disclosure of each of theforegoing cross-referenced United States Patent Applications isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates generally to implantable plates for usebone repair. More particularly, the present invention relates topolymeric plates having polymer molecule orientation for providingstrength and non-thermal bendability, and processes and systems forpreparing such polymeric plates.

2. The Related Technology

Bones are a vital skeletal feature and provide the frame and structuralsupport for holding associated muscles and other tissue. Additionally,bones, such as the skull bones and ribs, are responsible for protectingvital organs such as the brain, heart lungs, and the like. While bonesare structurally strong, they tend to break for various reasons whensubjected to excessive forces. Usually, the healing process includes amedical professional aligning the bones on each side of the break sothat the regenerated bone material provides a structurally sound mendedbone.

In addition to aligning the bone, various stabilizing techniques havebeen used to retain the broken bone in proper alignment during thehealing process. Traditionally, casts have been used to stabilize minorbreaks that do not need structural reinforcement at the bone. On theother hand, some complicated fractures or breaks can be susceptible tofalling out of alignment during the healing process. As such, plates,pins, bone nails, wires, fasteners, and the like can be used tostabilize the broken bones or fix bone structures. Use of these kinds ofstructural reinforcement systems during healing have been known toprovide bone regeneration and mending.

Due to excellent strength and stability profiles, metallic fasteners andplates have dominated the market for reinforcing breaks or fracturesduring healing. The most accepted metallic fasteners and plates arebiocompatible titanium and/or titanium alloys; however, other types ofmetallic materials have also been used. Nevertheless, metallic fastenersand plates can be problematic and have some disadvantages.

One disadvantage of implanted metallic fasteners and plates arises frombeing treated as a foreign body, which sometimes requires the fastenersand plates to be removed. This can occur even if the metallic fastenerand plate system is initially well tolerated. As such, the subsequentsurgery to remove the metallic fastener and plate system can causeadditional trauma to the patient, and adds additional costs to thehealth care system; especially when the patient has to be hospitalizedafter the procedure. Additionally, if the metallic fastener and platesystem includes an iron component, the irons released from the metallicimplant may be found in other organs, which can cause long-termproblems.

Another major disadvantage of metallic fastener and plate systems arisesfrom being much stronger than the bone being supported. As such, abroken bone that is fixed with a metallic fastener and plate system maynot experience proper loading during the healing process. This isbecause the metallic repair system can carry a large portion of the loadthat is normally carried by the bone. As a result, the bone can becomeweaker over time when the metallic repair system is left in place.Accordingly, after removal of the metallic repair system, the repairedbone may be susceptible to fracturing around the region that waspreviously supported. Even though the metallic repair system providesstructural reinforcement to the healing bone, the bone may developdecreased stability.

To overcome problems with metallic fasteners, fastener and plate repairsystems have been fabricated out of various polymeric materials that canbe configured into stiff and strong plates. In part, the vast array ofdifferent types of polymers have allowed for configuring the plate to bebiocompatible. However, a major disadvantage of known polymeric repairsystems arises during the implantation process. In contrast to metallicplates, polymeric plates typically cannot be plastically deformed inorder to conform to the bone being repaired. In order to achieveadequate bending, heat is often required to soften the polymericstructure and adapt the plate to precisely fit with the geometry of thebone. Numerous processes for heating the plates to allow for suchbending have been developed, which include hot air pistols, water baths,heat evolving pillows, laser energy, as well as many forms of heatedtips or biopsy instruments. While it is possible to heat and bend apolymeric plate, a significant disadvantage arises due to the additionaltime and instruments required to implement the surgical procedure.Furthermore, systems such as water baths might face sterility problems.

Additionally, the processes typically used to form fastener holes inpolymeric plates have caused anomalous features to develop, which areoften sites for potential catastrophic failure. This is because duringthe injection molding processes pins extend through the mold cavity ofthe mold to form the fastener holes. As such, the polymeric melt beinginjected into the mold cavity has to flow around the pins, which havesignificant diameters in order to accommodate various fasteners. Thiscan result in the melt separating into two melt flows that go aroundeach pin, and each resulting flow has a cooled front portion. When themelt flows that have separated around the pins come into contact again,the significantly cooled front portions of each flow merely weldtogether instead of providing a homogenous union. The lines that formwhere the different flows or cooled front portions contact each otheragain are called joint lines or dwelt lines. Joint lines are a place ofpotential catastrophic failure, especially when bending the plate.

Therefore, it would be advantageous to have a polymeric plate that isbendable or deformable without heat in order to be contoured to the bonebeing repaired. Also, it would be beneficial to have a polymeric platethat is configured to provide good initial strength and stability, butalso loses some mechanical strength over time so that the bone canself-repair to obtain proper strength and stability characteristics.

BRIEF SUMMARY OF THE INVENTION

Generally, an embodiment of the present invention includes a molded bodyfor use in preparing an implantable plate. Such a molded body includes atop surface having a portion being configured to be oriented outwardfrom the bone of the subject, and a bottom surface having a portionconfigured to be oriented inward toward the bone of the subject.Additionally, the body includes a recess defined by a recess surface,wherein the recess surface is adjacent to the top surface and extendsinto the body toward the bottom surface. Furthermore, the body caninclude a fastener hole template adjacent to a lower portion of therecess surface, wherein the fastener hole template is configured forbeing formed into a fastener hole that extends from the recess surfaceto the bottom surface. The hole template can be predrilled before asurgical procedure, or drilled during the surgical procedure.

Another embodiment of the present invention is an implantable plate forproviding support to a bone of a subject when affixed thereto. Such aplate can be comprised of a biocompatible polymer having a desiredamount of polymer molecule orientation in a first direction so that theplate can be bent to conform to a contour of the bone of the subject.Additionally, the plate includes at least one fastener portion at leastpartially defined by a portion of the top surface and a portion of thebottom surface. As such, each fastener portion includes a recess definedby a recess surface and a fastener hole that extends from a lowerportion of the recess surface to the portion of the bottom surface. Thefastener hole can be configured to receive a fastener when affixed tothe bone of the subject.

Another embodiment of the present invention can be a method ofmanufacturing an implantable plate as described above. Such a method caninclude injection molding a biocompatible polymeric composition so as toform a polymeric body within an injection mold, wherein the polymericbody can include at least a portion configured to be an implantableplate at least partially defined by a top surface and a bottom surface.Additionally, the method can include removing the polymeric body fromthe injection mold and forming at least one fastener hole within theimplantable plate portion.

These and other embodiments and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a block diagram illustrating an embodiment of a platefabrication system in accordance with the present invention;

FIG. 2 is a schematic diagram illustrating an embodiment of an injectionmolding apparatus in accordance with the present invention;

FIGS. 3A-F are cross-sectional schematic diagrams illustratingembodiments of injection mold gates in accordance with the presentinvention;

FIGS. 4A-C are top views illustrating embodiments of molded bodies inaccordance with the present invention;

FIG. 5 is a cross-sectional view illustrating an embodiment of a moldedplate in accordance with the present invention:

FIG. 6 is a cross-sectional view illustrating an embodiment of adrilling system in accordance with the present invention;

FIG. 7 is a top view illustrating embodiments of exemplary plates inaccordance with the present invention; and

FIG. 8 is a flow diagram illustrating an embodiment of a method forfabricating a plate in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention generally relates to implantable polymeric platesfor bone repair, and associated methods of manufacture. The presentinvention also relates to implantable plates prepared from abiodegradable polymeric composition that have high initial strengthafter implant, but degrade slowly over time so as to weaken in strength.

I. Bendable Polymeric Plates and Methods of Manufacture

In general, it is known that articles manufactured from polymers can beconfigured to have various degrees of polymer chain orientation. Polymerchain orientation describes the amount of polymer macromolecules thatare stretched or aligned in one direction. For example, applying a shearstress to a polymer composition can be used to create highly orientedpolymeric articles that can be deformed without heat. However, varioustypes of polymers that initially have high orientation may relax whenimplanted in the human body, which may cause the overall dimensions ofthe part to shrink or otherwise change dimensions. This can occur eventhough the body temperature is below the glass transition temperature ofthe polymeric material. Also, high levels of shear stress can alsodecrease orientation by causing the polymeric material to furtherincrease in temperature so as to randomize the polymers before they areset. While it may be beneficial to incorporate biodegradable polymersinto such parts, the biodegradation should be uniform and not cause theoverall length, width, or thickness to shorten and/or straighten overtime.

Accordingly, a polymeric plate that significantly shrinks and/orstraightens after it has been implanted into the human body is notacceptable because of the problems associated with the forces applied tothe mending bone. More particularly, high shrinkage in the direction ofpolymer molecule orientation tends to impart unfavorable stresses on theunderlying bone. Also, the temperature of the body can induce ashape-memory process that straightens the plates so that they no longerconform to the shape of the mending bone. Such shrinkage and/orstraightening of polymeric plates may be avoided by treating the plateat certain bending points with heat so as to increase the temperatureabove the softening point, glass transition temperature and/or meltingpoint, thereby allowing the polymer molecule orientation to relax. Onthe other hand, such shrinkage and/or straightening can be achievedwithout the aid of heat by configuring the initial polymer moleculeorientation to be in accordance with the present invention.

In one embodiment, a polymeric plate can be prepared by a process thatprovides a certain amount of polymer molecule orientation in order toallow the plate to be capable of bending without the use of heat. Assuch, it is possible to configure the plate to be capable of bending toangles of about thirty degrees or less. Also, the polymer moleculeorientation can be configured to be low enough so as to avoidunfavorable shrinkage and/or straightening after implantation.Additionally, the polymer molecule orientation can be configured toavoid any shrinkage and/or straightening after being bent into a shapethat conforms to the bone being reinforced. Moreover, the polymermolecule orientation can be configured to have enough directionalorientation to provide strength and flexibility to the plate so that itwill not break, fracture, or fatigue during the bending process.

In one embodiment, the plates can be fabricated by injection molding inorder to achieve a desired amount of polymer molecule orientation. Assuch, injection molding can be performed to impart a shear stress to thepolymer molecules that results in the desired amount of orientation,which is usually in the direction of the flow within the mold. As such,the runners, runner network, flow dividers, cold wells, gate regions,gates, mold cavity orientation, vents, mold temperature, polymercomposition, and flow rates can be manipulated and changed to achievethe desired amount of polymer molecule orientation.

In one embodiment, a polymeric plate can be prepared by a process thatincludes optimizing the level of polymeric molecule orientation. Assuch, optimizing the level of polymeric molecule orientation can beperformed in order to impart mechanical stability and bendability to thepolymeric plate. By optimizing the injection molding conditions (e.g.,polymer composition, mold configuration, polymer melt temperature, flowrates, gate configuration, shear stress, etc.), the process can providea plate that can be bent to a certain extent, while avoiding a platethat will undergo unfavorable shrinkage and/or straightening.Furthermore, optimizing the injection molding conditions can avoid theformation of unfavorable joint lines because they are a potential placeof catastrophic failure.

In one embodiment, a fabrication process provides increased platestability and bendability by including a combination of injectionmolding and mechanically drilling the fastener holes. The geometry andcomposition of the plate can be formed during the injection moldingprocess, which conforms to the shape of the cavity and polymers injectedtherein. The fastener holes are then mechanically drilled into the plateafter being injection molded. When the fastener holes are drilled afterinjection molding, joint lines can be avoided. In part, this is becausethe shear stresses in the longitudinal flow direction within of theplate are not disturbed by the presence of pins or other flow alteringfeatures.

Additionally, the injection molding process can be configured to includea gate that provides the desired amount of polymer molecule orientation.More particularly, the gate within the injection mold can be adapted toorient the molecules by the shear stresses that are imparted to thepolymeric melt when the injection mold cavity is being filled. A smallergate can provide a high shear stress and result in high polymer moleculeorientation; however, a gate that is too small can increase the shearstress past a favorable point and result in increased temperatures andrandomized polymer orientations. Also, larger gate can reduce the shearstress and result in low polymer molecule orientation. Accordingly, thesize of the gate can be modulated between small and large gates tooptimize the polymer molecule orientation without unfavorablyrandomizing the polymers. Other factors that can be modulated in orderto alter the polymer molecule orientation include, for example, melttemperature, mold temperature, injection rate, mold geometry, and thelike.

In accordance with the foregoing, various polymeric plate fabricationparameters can be balanced so as to provide a plate that may be testedin a 37° C. water solution in order to mimic implantation into the humanbody. As such, the resulting plate can be configured and fabricated tohave less than 5% shrinkage by volume or weight over a period of 10 daysafter being placed n a 37° C. bath.

II. Polymeric Compositions

Various types of polymers can be employed in preparing bendablepolymeric plates in accordance with the present invention. The polymerscan include a wide range of biocompatible materials that can beimplanted within body of a living animal, such as a human, dog, cat,horse, cow, and the like. Additionally, the polymers can be combined andblended in order to achieve compositions that have high initialstrengths, bendability, and can degrade within a living body over time.

In one embodiment, a polymer composition for use in injection molding abiocompatible plate can include at least one biodegradable polymer. Forexample, the biodegradable polymer composition can include at least oneof poly(alpha-hydroxy esters), polylactic acids, polylactides,poly-L-lactide, poly-DL-lactide, poly-L-lactide-co-DL-lactide,polyglycolic acids, polyglycolide, polylactic-co-glycolic acids,polyglycolide-co-lactide, polyglycolide-co-DL-lactide,polyglycolide-co-L-lactide, polyanhydrides, polyanhydride-co-imides,polyesters, polyorthoesters, polycaprolactones, polyesters,polyanydrides, polyphosphazenes, polyester amides, polyester urethanes,polycarbonates, polytrimethylene carbonates,polyglycolide-co-trimethylene carbonates, poly(PBA-carbonates),polyfumarates, polypropylene fumarate, poly(p-dioxanone),polyhydroxyalkanoates, polyamino acids, poly-L-tyrosines,poly(beta-hydroxybutyrate), polyhydroxybutyrate-hydroxyvaleric acids,combinations thereof, or the like. Additionally, these polymers can beused at a wide range of molecular weights, which can range from lessthan about 25,000 MW to over 1,000,000 MW. More particularly, themolecular weight can vary depending on the type of polymer, initialstrength, plate bendability, degradation rate, and the like. Additionalinformation on the tensile strength, tensile modulus, flexural modulus,and elongations at yield and at break of various biocompatible andbiodegradable polymers can be found with Engelberg and Kohn;Physico-mechanical Properties of Degradable Polymers Used in MedicalApplications: A Comparative Study; Biomaterials; 1991; 12:292-304, whichis incorporated herein by reference.

In one embodiment, a polymer composition for use in injection molding abiocompatible plate can include at least one inert polymer. For example,the inert polymer can include at least one of high-densitypolyethylenes, ultra-high-density polyethylenes, low-densitypolyethylenes, polypropylenes, polyacrylates, polymethylmethacrylates,polyethylmethacrylates, polysulfones, polyetheretherketones,polytetrafluoroethylenes, polyurethanes, polystyrenes,polystyrene-co-butadienes, epoxies, and the like. Such inert polymerscan be used at a wide range of molecular weights in order to impartvarious mechanical strengths and bendabilty to the polymeric plate.

In one embodiment, the polymer composition for use in injection moldinga biocompatible plate can include at least one natural polymer that canbe derived from a natural source. Natural polymers can includepolysaccharides, proteins, and the like. Examples of some suitablepolysaccharides include methylhydroxyethylcellulose,hydroxymethylethylcellulose, carboxymethylcellulose, methylcellulose,ethylcellulose, hydroxyethylcellulose, hydroxyethylpropylcellulose,amylopectin, amylose, seagel, starches, starch acetates, starchhydroxyethyl ethers, ionic starches, long-chain alkylstarches, dextrins,amine starches, phosphate starches, and dialdehyde starches, alginicacid, phycocolloids, agar, gum arabic, guar gum, locust bean gum, gumkaraya, gum tragacanth, and the like. Examples of some proteinaceousmaterials include collagens, caseins, and the like. Moreover, thesenatural polymers can also impart biodegradable characteristics to theplate.

In one embodiment, the biodegradable polymers can be reinforced withfibers comprised of magnesium, wherein such fibers can significantstrength the plates. For example, short fibers, which are added to thepolymer during the injection molding process, can be oriented in thedirection of the flow so as to significantly improve the mechanicalproperties, such as strength and the plate's ability to bend.Additionally, the magnesium fibers can be pretreated with corona plasmaor other well-known method to improve the interface between the polymersand fiber. Since pure magnesium can be highly reactive with water orbody fluids, the polymer matrix can act as a shield and protect againstfast degradation and magnesium reactions. It can also be understood thatoptionally the plate can be formed completely from magnesium andsubsequently coated with a polymer coating to shield and protect againstfast degradation.

In one embodiment, short fibers of biodegradable micro or nano-poroussilicon materials, biodegradable ceramics, organic materials can beadded to the polymer. The short fibers, which are added to the polymerduring the injection molding process, can be oriented in the directionof the flow and significantly improve the mechanical properties, such asstrength and the plate's ability to bend, of the resulting plate.Optionally, these degradable fibers can be pretreated with corona plasmaor other well-known method to improve the interface between the polymermatrix and the fiber. Also, the rate of fiber biodegradation can beslowed by being encapsulated within the polymer matrix.

The addition of fibers into the implantable plate can improve many ofthe mechanical or strength characteristics of the implantable plate. Inpart, this can arise from the nature of the fibers, and/or beingoriented with the polymer molecules. For example, the fibers canincrease the Young's modulus, increase the strength, and decrease theshrinkage.

In one embodiment, the biodegradable polymers, inert polymers, naturalpolymers, magnesium fibers, and/or porous silicon fibers can be preparedinto a polymeric blend that is comprised of different types of polymersand materials. As such, a polymeric blend can be configured to achieveinjection moldability, polymer molecule orientation, high initialstrength, and bendability. Moreover, the biodegradable polymers and/ornatural polymers can be blended in order to achieve biodegradable platesthat can degrade over time after being implanted.

In another embodiment, the plate can be fabricated from biodegradablemicro or nano-porous silicon materials, biodegradable ceramics, ororganic materials. Optionally, the plate made from one or more of thesematerials and ceramics can be coated or covered with a polymer orpolymer matrix.

In yet another embodiment, the biodegradable polymers of the plate canbe admixed with a drug for being delivered into the body afterimplantation. This can include mixing a drug into the polymercomposition before being injection molded, or applying a drug-containingpolymeric coating onto the implantable plate. In any event, a portion ofthe implantable plate, either the bulk biodegradable polymer or abiodegradable coating can be configured to deliver drugs into the bodyafter being implanted. Accordingly, any drug can be included into theimplantable plate, especially analgesics, anti-inflammatory,anti-microbial, and like drugs.

III. Implantable Polymeric Plate Fabrication System and Process

In one embodiment, a fabrication system and process can be employed toprepare implantable plates having features in accordance with thepresent invention. Such a fabrication system includes the use of aninjection mold configured to prepare polymeric implantable plates havingthe characteristics described herein, and the use of a drilling systemto form faster holes in the implantable plates. An exemplary platefabrication system and process is described in more detail below.

FIG. 1 is a schematic diagram illustrating an embodiment of a platefabrication system 10 in accordance with the present invention. Ingeneral, the plate fabrication system 10 is configured to yield animplantable plate for structurally reinforcing a bone of a subject whenaffixed thereto. The plate fabrication system 10 can include a mixer 12configured to receive polymeric materials, such as biodegradable and/orinert polymeric materials, in order to form a substantially homogenouspolymeric composition. Additionally, the mixer 12 can be configured toreceive other types of polymeric materials, plasticizers,rheology-modifying agents, fillers, and the like in order to providevarious other characteristics to a polymeric plate fabricated with theplate fabrication system 10.

Optionally, the plate fabrication system 10 can include an extruder 14.As such, the polymeric composition mixed and formulated within the mixer12 can be supplied into the extruder 14 for further mixing, compacting,heating, and/or extruding. The extruder 14 can be a single screwextruder, double screw extruder, or piston-type extruder. Additionally,the extruder 14 can include heating elements in order to take advantageof the thermoplastic characteristics of some embodiments of thepolymeric composition and heat the composition past its softening point,melting point, and/or glass-transition temperature. In any event, theextruder 14 can extrude the composition through a die head to anextrudate of any shape, which can optionally be pelleted beforeinjection molding.

After being extruded from the extruder 14 or mixed within the mixer 12,the polymeric composition can be introduced into a pre-mold 20. Thepre-mold 20 is a compartment, container, tube, conduit, injection line,hopper, or the like in fluid communication with the injection mold 22that can hold the polymeric material before being injection molded.Alternatively, the composition can be provided directly into theinjection mold from the extruder 14 or mixer 12.

Additionally, a dryer 16 can dry the polymeric material while in thepre-mold 20. Sometime the polymeric material can absorb moisture duringprocessing, wherein the moisture can be counter-effective to a resultingplate; especially when a biodegradable polymer, which can cause theplate to prematurely degrade. As such, the dryer 16, can be configuredto remove moisture from the polymeric material.

Additionally, a pressurizer 18 can pressurize the pre-mold 20 so thatpolymeric composition can be injected into the injection mold 22 underhigh pressure. In any event, dryer 16 and pressurizer 18 may be optionalbecause the pre-mold 20 and/or the injection mold 22 may be outfittedwith such components in order to provide these functionalities. Also,various other well-known injection molding equipment may be utilized inconjunction with the pre-mold 20 so as to prepare the polymericcomposition for injection molding.

In any event, the polymeric composition can be injected into theinjection mold 22 in order to prepare the implantable plate. Usually,the process includes injecting the polymeric composition under highpressure and/or heat so that the composition can flow through thevarious pathways and compartments within an injection mold. This allowsthe polymeric composition to be injection molded into an article ofmanufacture such as the implantable plate, as described in furtherdetail below.

Optionally, the molded article prepared from the polymeric compositioncan be removed from the injection mold 22 and moved into a post-mold 24.Such a post-mold can be any component within an injection molding systemthat receives the molded article in a heated or otherwise freshly moldedform so that it can be conditioned for further processing.Alternatively, the post-mold can be the state of the mold bodycontaining the molded article after injection molding is complete.Accordingly, the post-mold 24 can be coupled with, or in fluidcommunication with, a cooler 26 to provide cool air or other coolingfluid for decreasing the temperature of the molded article. Cooling themolded article can increase form-stability and ease of handling.Additionally, the post-mold 24 can include various other well-knowncomponents in injection molding systems in order to prepare a moldedarticle for further processing. Alternatively, the molded article can beremoved from the mold and flushed with an inert gas. This can aid inconditioning the polymer for further processing or implantation.

It will be understood that the functionality of one or more of theinjection mold 22, the post-mold 24, and the cooler 26 can optionally becombined when a cooled injection mold 22 is used to create the moldedarticle. For instance, a water, air, or fluid cooled injection mold 22can be used to fabricate the molded article of the present invention.

After being sufficiently prepared for further processing, the moldedarticle can be introduced into the drilling apparatus 28. The drillingapparatus 28 can be configured to include various mechanisms andassemblies in order to align the implantable plate in the properorientation so that fastener holes can be formed. The drilling apparatus28 can form the fastener holes by drilling, milling, stamping, punching,laser machining, and the like. In any event, the drilling apparatus 28can be configured to precisely drill holes within the plates.

Optionally, the molded article can be processed with an optional tapassembly 30. Such a tap assembly 30 can include taps in order to formthreads on the inner wall of any of the holes drilled in the plate. Assuch, the holes in the implantable plate can be threaded so as tointeract or interlock with the threads of a screw, bolt or otherfastener when securing the implantable plate to the bone of the subject.The tap assembly 30 can be optional because some embodiments of thepresent invention do not require such threaded holes in order for properfunctionality.

Before or after the fastener holes are formed, the plate can beintroduced into a separator assembly 32. Molded bodies typically includevarious irregularities in the external surface that arise from theinjection molding system and mold bodies. Also, when cold runnerinjection molding is utilized, the molded body can include runners,vents, junctions, dividers, cold wells, and other injection molding sideproducts that need to be removed from the plate before it can beutilized for its designed function (i.e., implantation and boneaffixation). As such, the separator assembly 32 can be configured withmechanic features in order to receive the molded body, and remove thevarious excess polymeric materials from the plate. Accordingly, theseparator assembly 32 can use cutters, stamps, punches, and/or othertechniques to remove the extra material away from the implantable plate.Thus, after being processed through the separator assembly 32, thepolymeric plate can be substantially shaped for implantation.

Additionally, the polymeric plate outfitted with fastener holes can beintroduced into a finishing assembly 34. Such a finishing assembly 34can be configured to finish the plate and place it in the properconfiguration for being implanted and affixed to a bone of a subject.This can include applying extra coatings of material onto of thepolymeric plate, re-surfacing some of the edges of the plate, or otherwell-known finishing techniques for enabling implantation.

While general features of a plate fabrication system 10 have beendescribed in connection with injection molding, various other similarprocesses or techniques can be utilized in order to prepare theimplantable plate in accordance with the present invention. Accordingly,various modifications to the foregoing process can be made to includeany well-known injection molding equipment, systems, and processes.Additionally, some of the foregoing components within such a platefabrication system 10 will be described in more detail below.

IV. Injection Molding

In one embodiment of the present invention, the system and process forpreparing an implantable plate employs an injection molding system. Aninjection molding system has the benefits of being configured to includecertain features for obtaining proper polymer molecule orientation inorder to achieve implantable plates having the strength and flexibilityas described herein. An exemplary injection mold is described in moredetail below.

FIG. 2 is a schematic diagram illustrating an embodiment of an injectionmold apparatus 50. The injection mold 50 can be configured to be usableas the injection mold 22 of FIG. 1. Accordingly, the injection mold 50can be capable of forming molded bodies from thermoplastic materialsthat have been processed and/or conditioned for proper injectionmolding. The injection mold 50 includes various components and featuresin order to form an injection molded article such as the implantableplate.

Accordingly, the injection mold 50 includes a mold 52. The mold 52 canbe comprised of a first mold body 54 and a second mold body 56. Thefirst mold body 54 can be configured to be aligned and compatible withthe second mold body 56. This allows the first mold body 54 and thesecond mold body 56 to come together and form a mold cavity 80 in theshape of the molded article. As such, each of the first mold body 54 andsecond mold body 56 includes various components and features thatcooperate for functioning as the injection mold 50.

The mold 52 includes pin holes 58 a-b to hold pins 60 a-b for enablingopening and closing. As illustrated, the pin holes 58 a-b extend throughthe first mold body 54 and into the second mold body 56. In order tofunction, the pin 60 a-b can be inserted into the pin aperture 62 a-band through second mold body 56 before being inserted through pinaperture 62 c-d of first mold body 54. This configuration allows firstmold body 54 and second mold body 56 to combine into the mold 52, andthe separation of first mold body 54 from second mold body 56 in orderto be able to extract molded article therefrom. A mechanical feature(not shown) operates in conjunction with pins 60 a-b, first mold body54, and second mold body 56 for facilitating the opening and closing ofthe mold 52 for injection molding and extracting the injection moldedarticle therefrom. Moreover, various types and configurations ofmechanical features are well known in the art and are considered to beincluded within the scope of the present invention.

Additionally, the mold 52 includes a runner inlet 66. For example, arunner inlet 66 can be present in a variety of dimensions such as adiameter or cross-sectional length of about 2 mm to about 5 mm or inother configurations from about 3 mm to about 4 mm. As used herein, theterm “cross-sectional length” is meant to refer to the diameter of acircular cross-sectional area or width of polygonal cross-sectionalarea. The runner inlet 66 can be configured and oriented to receive aflow of thermoplastic polymer into the runner 68 or a runner network.Runners 66 can also range in dimensions, and can be present with adiameter or cross-sectional length of about 1 mm to about 3 mm.Typically, a major runner 68 can be about 2 mm to about 3 mm, wherein arunner that feeds a cavity can range from about 0.75 mm to about 1.5 mm.In other configurations, the diameter or cross-sectional length of afeeding runner can range from about 1 mm to about 1.2 mm or be about 1.1mm. The runner 68 provides a conduit for the thermoplastic flow ofpolymeric materials to be properly distributed throughout the mold 52and more specifically, into the mold cavity 80. The runner 68 can beconfigured to either be a cold runner or a hot runner.

When a cold runner, a polymeric runner can be formed as part of themolded article, which is cooled and injected with the molded plate. In ahot runner mold, the runner 68 is situated internally in the mold andkept at a temperature above the softening or melting point of thepolymeric composition. As such, runner scrap can be eliminated orreduced with use of a hot runner.

In one embodiment, the runner 68 can provide a flow of thermoplasticpolymers into multiple cavities 8 a-d. In this instance, mold 52includes a divider 70 to separate the flow. Often, the divider 70 can beplaced at a junction of multiple runners 68 so that the flow ofpolymeric material can be directed towards any of the various cavities80 a-d within the mold 52. Additionally, the divider 70 can be incommunication with a cold well 72. Such a cold well 72 can be a pocketor a cavity within the mold 52 that allows for the front or cooledportion of the thermoplastic melt to be trapped and not processed intothe molded article. As such, providing for various cold wells 72 at theend of various runners 68 can provide a space for the somewhat harder,cooler, or solidified polymeric material to be trapped.

In one embodiment, the mold 52 includes a gate region 76 a-d. As such,each cavity 80 a-d includes a gate region 76 a-d between the cavity andthe corresponding runner 68 or divider 70 so that the polymeric materialflows through a gate region 76 a-d. A gate region 76 a-d can beconfigured to constrict or expand the thermoplastic flow. For example, agate region 76 a-d can be designed to constrict the flow from a largerunner to a small gate 78 a-d, wherein the angle of constriction can beabout 10 degrees to about 90 degrees. In other configurations, the angleof constriction can range from about 30 degrees to about 75 degrees orbe about 60 degrees.

Additionally, each gate region 76 a-d includes a gate 78 a-d. Each gate78 a-d can be configured to impart some shear stress to thethermoplastic flow as it enters the cavity 80 a-d. With that said, eachgate 78 a-d can be configured for each type of polymer flow in order toprovide the proper polymer molecule orientation to the molded article.The gate 78 a-d can have various shapes, sizes, and dimensions toprovide properly aligned or oriented polymers in the molded articles.For example, the gate 78 a-d can be configured to have a diameter orcross-sectional length that ranges from about 0.2 mm to about 1 mm. Inother configurations, the diameter or cross-sectional length of the gate78 a-d can range from about 0.3 mm to about 0.9 mm or about 0.4 mm toabout 0.8 mm. More specifically, configuring gate 78 a-d can allow for auser to fabricate molded articles with a precise amount of polymermolecule orientation for structural fitness and function as animplantable plate.

In any event, the thermoplastic material will flow through gate region76 a-d and through each corresponding gate 78 a-d before beingintroduced into a mold cavity 80 a-d. The cavity 80 a-d can beconfigured to be a void within the mold 52, and can be formed withoutany protrusions or flow disrupting formations.

Previously, injection molding systems have utilized various protrusionsor features that extend through the mold cavity and result in flowdirectors that disrupt the polymer molecule orientation or cause eddieswithin the thermoplastic flow. The protrusions or other features thatextend through the mold cavity have been used to create holes withinsuch molded plates for receiving screws or other fasteners to secure theplate to the bone. However, the use of protrusions extending through thecavity have provided for structural problems within the molded articlesbecause as the flow of material moves around each pin it comes togetherto form a joint line. Such joint lines are well known to be a source offatigue and ultimate catastrophic failure when the plates are beingused. The formation of joint lines or dwelt lines within a molded plateis unfavorable, and avoided by a cavity that does not include suchfeatures or pins that disrupt the thermoplastic flow. By having an openmold cavity, a molded plate can be fabricated with proper polymericorientation to provide a strong and bendable implantable plate, asdescribed in more detail below.

Additionally, in order to eliminate the pressure that can build upwithin a cavity 80 by the front of a thermoplastic flow, the cavities 80a-d can include a plurality of air vents 82 a-e. Such air vents 82 a-eare usually small in size so that air within the cavity 80 a-d can beremoved without a significant portion of the thermoplastic melt alsoflowing therethrough. Alternatively, the air vents 82 a-c can have asubstantial dimension in order to allow the flow of material to passthrough, which can enhance the uniform polymer molecule orientation andresult in a strong and bendable molded plate.

While one embodiment of an injection mold has been illustrated anddescried, various other configurations and orientations of well-knowninjection molds can be employed. For example, the injection moldingapparatus 50 can be comprised of a two body or three body mold, and canbe operated with cold or hot runners. Additionally, variousmodifications can be made to the exemplary mold described herein.

V. Gate Design

In one embodiment of the present invention, an injection mold can bedesigned with gates that direct and orient the polymeric molecules in amanner that provides the strength and flexibility characteristics asdescribed. More specifically, the gate dimensions and shapes can beoptimized in order to provide directional alignment for a certainpercentage of the polymer molecules. As such, the gates can be designedto cooperate with the polymer composition, thermoplastic flow rate, andother injection molding parameters in order to prepare an implantableplate with the strength for such use and the ability to flex or bend theplate so as to conform to the shape of the underlying bone. Exemplarygate designs are for providing polymer molecule orientation aredescribed in more detail below.

FIGS. 3A-F illustrate embodiments of a gate 100 a-f that can be usedwithin the injection mold 50 of FIG. 2. Such gates 100 a-f areconfigured to provide the proper orientation of the polymer moleculeswithin the thermoplastic composition and the resulting implantableplate. With that said, the various embodiments of the gates 100 a-f willbe described below.

FIG. 3A depicts one embodiment of a gate 100 a, which cooperates with athermoplastic composition in order to provide proper orientation to thepolymeric molecules. As such, gate 100 a includes a gate aperture 102that is defined by a first gate wall 104 a of a first mold body 106 aand a second gate wall 104 b of a second mold body. When the first moldbody 106 a and the second mold body 106 b come together to form a moldbody junction 105, a uniform gate wall 104 a-b is formed to define thegate aperture 102. While a square gate aperture 102 bisected by the moldbody junction 105 is illustrated and described herein, various othershapes, conformations, and orientations can be utilized. Also, variousdimensions and other aperture surface areas can be used in order toprovide the proper orientation of the molecules; especially a narrowingor expanding gate region on either side of the gate aperture 102.

FIG. 3B depicts one embodiment of a gate 100 b, which includes a gateaperture 108 that is defined by a first gate wall 110 a of a first moldbody 112 a and a second gate wall 110 b of a second mold body 112 b.Accordingly, when the first mold body 112 a comes together with thesecond mold body 112 b to form a mold body junction 111, the first gatewall 110 a comes together and joins with the second gate wall 110 b todefine the gate aperture 108. In this embodiment, the mold body junction111 is on one end of the gate aperture 108 so as to illustrate that theorientation and/or placement of the gate aperture 108 with respect tothe first mold body 112 a and the second mold body 112 b can be variedand still provide the proper orientation to the polymeric molecules.

FIG. 3C depicts one embodiment of a gate 100 c which includes a gateaperture 114 having a narrow and vertical orientation. The gate aperture114 is defined by a first gate wall 116 a of a first mold body 118 a anda second gate wall 116 b of a second mold body 118 b. When the firstmold body 118 a and second mold body 118 b form the mold body junction117, the first gate wall 116 a and second gate wall 116 b cooperate todefine the narrow and vertical gate aperture 114. A narrow verticalorientation can be preferred in some instances to provide increasedpolymer molecule orientation. As such the dimensions of gate aperturecan be changed to have different sizes or cross-sectional areas in orderto provide the proper polymer molecule orientation.

FIG. 3D depicts one embodiment of a gate 100 d that includes a gateaperture 120 that is characterized by having a substantially horizontalcross-sectional area that is bisected by a first mold body 124 a and asecond mold body 124 b. More specifically, the gate aperture 120 isdefined by a first gate wall 122 a, and the second gate wall 122 b. Asbefore, when the first mold body 124 a comes together with the secondmold body 124 b, the first gate wall 122 a cooperates with the secondgate wall 122 b in order to perform the gate aperture 120. A wide gateaperture 120 can be preferred in order to provide lower polymer moleculeorientation.

FIG. 3E depicts one embodiment of a gate aperture system 100 e that ischaracterized by having a plurality of gate apertures 128 a-d. As such,in place of a single gate aperture, a plurality of gate apertures 128a-d can be utilized to provide the proper polymer molecule orientation.Similar with the foregoing gate apertures, the gate aperture 128 a isdefined by a first gate wall 130 a of a first mold body 132 a and a by asecond gate wall 129 a of a second mold body 132 b. Similarly, the gateapertures 128 b-d are defined by the first gate walls 130 b-d of thefirst molded body 132 a and by the second gate walls 129 b-d of thesecond mold body 132 b. While a four aperture gate system 100 e isillustrated and described, various other numbers of apertures can beused to provide the proper polymer molecule orientation.

FIG. 3F depicts one embodiment of a gate 100 f that includes a gateaperture 134 oriented within a first mold body 138 a. As such, the gateaperture 134 includes a gate wall 136 which is completely defined byfirst mold body 138 a. While mold body junction 140 separates the firstmold body 138 a from the second mold body 138 b, it does not define anyportion of gate aperture 134. This gate configuration allows for uniquegate aperture orientations and placement with respect to the moldcavity. Also, by orienting the gate aperture within only one molded bodythe polymer molecule orientation can be enhanced for certainembodiments.

While various shapes, orientations, and configurations of gates 100 a-fhave been illustrated in FIGS. 3A-F, various changes to the dimensions,cross-sectional area, shape, and number of the apertures can be made inaccordance with the present invention. This allows for a mold to beprepared with unique shapes and/or sizes that cooperate with thethermoplastic polymer compositions and flow rates in order to obtainproper polymer molecule orientation within the finished molded article.Examples of some cross-sectional shapes include circles, rectangles,squares, octagons, pentagons and the like, wherein various polygons canbe used in order to provide the proper polymer molecule orientation.Additionally, a gate aperture diameter or cross-sectional length fromabout 10% to about 60% of the mold cavity average cross-sectional length(diameter) or runner cross-sectional length (diameter) can provideoptimal polymer orientation. In other configurations the gate aperturediameter or cross-sectional length can range from about 20% to about 50%or from about 30% to about 40% of the mold cavity averagecross-sectional length (diameter) or runner cross-sectional length(diameter).

In one embodiment, any of the gates 100 a-f described herein can befabricated as an independent component, or with a corresponding gateregion, that can be removably inserted into an injection mold. That is,a single injection mold can be configured to include and/or receiveinterchangeable gates and/or gate regions. This allows for an injectionmold to be modified between molding procedures in order to alter thepolymer molecule orientation. As such, a predetermined gate andpolymeric composition combination that provides the proper polymermolecule orientation can be utilized together during a moldingprocedure. As such, various other modifications to the foregoingembodiments of a gate can be made within the scope of the presentinvention as long as proper orientation of the polymeric moleculeswithin a specific polymeric composition can be obtained.

VI. Molded Bodies

In one embodiment, the foregoing processes and systems can be employedto prepare molded bodies that include at least one portion configured tobe an implantable plate. Additionally, the molded bodies are generallyshaped to conform to the features of the mold cavity from which theywere prepared. Exemplary molded bodies are discussed in more detailbelow.

FIGS. 4A-C illustrate various embodiments of molded bodies 150 a-cprepared in accordance with the present invention. More particularly,the molded bodies 150 a-c are prepared by an injection mold 50 of FIG.2. Accordingly, the injection mold 50 of FIG. 2 can be configured sothat the cavities 80, runners 68, and the like provide the shapes andfeatures shown on each of the molded bodies 150 a-c described herein.Additionally, the cavity that forms the molded body 150 a-c is devoid ofany features that would separate the thermoplastic flow and allow for itto rejoin and form joint lines, which is shown by the plate body 172being devoid of any holes as will be discussed below.

With specific reference now to FIG. 4A, a molded body 150 a isillustrated and described. Such a molded body 150 a includes a runnerinlet 152 a and runner network 154 comprised of runners 154 a-b, whichcan be formed by the runner in the mold solidifying with the polymericcomposition. Additionally, each runner 154 a-b terminates at a runnerdivider 156 a-b that is adjacent to a cold well 158 a-b. Also, eachrunner divider 156 a-b portion of the molded body 150 a can be adjacentto a gate region 160 a-d that includes a gate 162 a-d. Each gate 162 a-dcan be connected to a plate body 172, which can be the 4-lock plate 164,8-lock plate 166, 6-lock plate 168, and 4-lock plate 170. Additionally,each plate body 172 can be comprised of a plate recess 174 and holetemplate 176, and can be also connected to a vent 178 that formed fromthe thermoplastic flow entering a cold well 180. In some instances, therecess can be the hole template. Thus, the injection mold thatfabricates the mold body 150 a includes each and every feature that isdepicted.

Additionally, the plate body 172 can be devoid of holes configured forreceiving a fastener, which indicates that the corresponding mold can bealso devoid of pins or protrusions extending through the cavity thatwould form such fastener holes. This is because the injection mold andmold cavity are configured to receive the thermoplastic flow in a mannerthat does not form joint lines. Thus, the cavity has an openconfiguration that inhibits joint formation by not having any featuresthat separate the thermoplastic flow and allow for two cooled fronts tojoin back together.

FIG. 4B illustrates another embodiment of a molded body 150 b thatincludes various features provided by a mold. As before, the molded body150 b includes a runner inlet 152 b and a runner network 154 comprisedof a plurality of runners 154 c-g. Additionally, the molded bodyincludes dividers 156 c-d adjacent to the cold wells 158 c-d, and aplurality of gate regions 160 e h and gates 162 e-h at the ends of therunner network 154.

The molded body 150 b also includes a 4-lock plate 182, 8-lock plates184 and 186, and 12-lock plate 188 connected to the gates 162 e-h. Incontrast to molded body 150 a that includes one vent 178 and one coldwell 180 for each plate body 182-188, molded body 150 b includes aplurality of vents 190 a-d for each plate body 182-188. Additionally,each of the plurality of vents 190 a-d opens into a cold well network192 a-d that has an air vent 194 a-d.

Accordingly, the molded body 150 b can be formed by the thermoplasticmelt flowing into the cavity as with 150 a. Additionally, the presenceof the plurality of vents 190 for each plate body 182-188 that opensinto a cold well network 192 allows for the thermoplastic melt to flowthrough the cavity without pressure building up. As such, the airescapes through the vent 190 via the cold well network 192 and outthrough the air vents 194. This configuration allows the thermoplasticflow to fill the cavity as well as the cold well network 192 as shown.In part, this configuration along with a properly designed gate 162allows for proper polymer molecule orientation as described herein.

FIG. 4C depicts another embodiment of a molded body 150 c, whichincludes many of the features described in connection with molded bodies150 a and 150 b. Additionally, the molded body 150 c can be configuredinto a non-bendable or non-degradable implantable plate. Molded body 150c differs by having a plurality of gates for each plate body as shown.As such, the 4-lock plate 198 includes a 4-gate system 200 a-d; the2-lock plate 202 includes a 2-gate system 204 a-b; and the 6-lock plate206 includes a 6-gate system 208 a-f. In this configuration each cavitythat forms a plate includes a plurality of gates so that thethermoplastic melt can enter each mold cavity at various locations. Thismold configuration differs from including pins or other flow divertingfeatures because the plurality of gates allow for the proper orientationof the polymeric molecules. When the polymer enters the cavity atvarious locations, minimal to no joints form because of the open-voidnature of the cavity, which provides for homogenous distribution andproper orientation of the polymeric molecules.

While various features and embodiments of molded bodies have beendescribed in connection herewith the FIGS. 4A-C, various other featuresand embodiments can be used. As such, molded bodies can be altered orchanged to have various shapes and conformations and not depart from thespirit and scope of the present invention. Additionally, FIGS. 4A-C notonly depict and describe molded bodies, but also the requisite featuresof mold in order to provide such molded bodies.

Referring now to FIG. 5, certain features of an embodiment of a moldedplate 250 are illustrated and described. The molded plate 250 caninclude the features as previously described in connection with FIGS.4A-C. More specifically, the molded plate 250 can include a plate body252 comprised of a plate surface 256, recess surface 258, and holetemplate 260. The recess surface 258 defines a recess 254 that includesthe hole template 260 at its base. Accordingly, the plate recess 254 andplate surface 256 are configured be compatible with the shape of a screwbolt or other fastening means. That is, a screw or other fastener canprecisely fit into a plate recess 254 so it does not protrude above andover the plate surface 256.

The hole template 260 can be included at the bottom of the plate recess254 and has the proper size and orientation in order to be drilled so asto form a hole. Alternatively, the recess can be the hole template.Moreover, the hole template can be a raised portion, annular ridge,indicia, and the like with or without being at the base of a recess solong as the placement of the hole is demarked upon the body of the plateby the hole template. When a hole is formed into the hole template 260,it provides a conduit for a fastener to be inserted and affix the moldedplate 250 to a bone of a subject.

While embodiments of molded bodies have been depicted and described inconnection with the present invention, other molded bodies having thedesired polymer molecule orientation can be used. This can includemolded bodies without any of the foregoing features such as recesses andhole templates. As such, a generally shaped molded body without a recessor hole template can be prepared so that subsequent processing can formthe recesses and/or fastener holes.

VII. Drilling Polymeric Plates

In one embodiment of the present invention, a process for preparing animplantable plate includes drilling or otherwise forming holes forreceiving a fastener. In exemplary embodiments, the fastener holes areformed by drilling through the hole templates in the molded body.Alternatively, the fastener holes can be formed by drilling at anylocation on a plate. Additional details of drilling system are describedin more detail below.

FIG. 6 depicts features of an embodiment of a drilling system 270 inaccordance with the present invention. Such a drilling system 270 can beutilized within the drilling apparatus 28 of FIG. 1. The drilling system270 can include a drilling device 272 configured to have the propermechanics and components in order to provide the drilling functionality.As such, the drilling device 272 includes a drill bit holder 274 withinthe drill bit opening 278 configured hold a drill bit 276 whileperforming the drilling function. Additionally, drilling system 270 caninclude well-known automation in order to provide automated drilling.

As depicted, molded plate 279 includes a plate recess 280, which can beat least partially defined by the recess surface 282. This can providefor alignment and orientation of the drilling device 272, and morespecifically, for the drill bit 276 to be aligned with respect to thebit entrance 284. The bit entrance 284 can be substantially the same asthe hole template as previously described; however, the bit entrance 284is the precise site that the drill bit 276 drills into to the moldedbody 279. Alternatively, the recess 280 or any portion of the moldedplate 279 can be the hole template, and hence the bit entrance 284. Thedrill bit 276 then forms the hole 286 within the molded plate 279. Afterdrilling completely through the molded plate 279, the drill bit 276exits the bit exit 288. Thus, the drilling system 270 can form a hole276 for receiving screws, bolts or other fastening means in order tofasten the molded plate to the bone of a subject.

In one embodiment, the automation can be used to orient and form thefastener holes. As such, a molded body without a recess or hole templatecan have fastener holes formed therein. That is, the automation canreceive and/or orient the molded body in a position that enables thefastener holes to be drilled without any recess or hole template. Thiscan include drilling a recess and/or drilling the fastener hole withoutany guidance provided by the molded body.

While one embodiment of a drilling system has been depicted anddescribed, other drilling systems can be employed. Such drilling systemscan include punching, milling, stamping, laser machining and likehold-forming equipment.

VIII. Implantable Polymeric Plates

In one embodiment of the present invention, the molded plates preparedby the foregoing systems and processes can be fabricated intoimplantable plates. Such implantable plates are usually separated from ageneral molded body before or after the fastener holes are formed.Additionally, the plate can be further processed as described herein inorder to be properly finished for implantability. Exemplary plates aredescribed in more detail below.

With reference now to FIG. 7, various embodiments of exemplaryimplantable plates 300 are illustrated and described. Briefly, the platefabrication system of FIG. 1 can produce the exemplary implantableplates 300. The exemplary implantable plates 300 are represented by a2-lock plate 302, T-plate 304, 4-lock plate 306, arc-plate 308, H-plate310, L-plate 312, and Y-plate 314. More details of the features of suchexemplary plates 300 are provided below.

In one embodiment, each of the plates 302-314 can be defined by a platebody 316 comprised of a lock portion 317 and a spacer region 324. Forexample, the 2-lock plate 302 includes a lock portion 317 with a recess318 adjacent with a fastener hole 320. The fastener hole 320 can bedefined by a hole surface 322, and provides a conduit for receiving afastener, such as a screw or bolt, in order to attach to the 2-lockplate 302 to the bone of a subject. Additionally, the spacer region 324can be of any shape and dimension, and is not strictly limited to thoseillustrated and described herein. Also, the spacer region 324 can beextended to provide for any distance between respective fastener holes320. Furthermore, some embodiments of plates 300 can include a junctionregion 328 that provides for the intersection of various arms 326, whichcan be exemplified by the T-plate 304, L-plate 312, and Y-plate 314.

While various plates with junctions 328 and arms 326 are illustrated anddescribed, exemplary plates 300 can also be formed as rectangularplates, square plates, circular plates, and other polygonal shapes aswell as custom or novel shapes. Additionally, the exemplary plates 300can have any number of fastener holes 320 in any orientation orposition. Thus, the plates of the instant invention are not limited inshape or size or fastener hole, and can be fabricated into any known orfuture developed implantable conformation.

Additionally, the foregoing implantable plates can be fabricated withbiodegradable polymers in order to degrade slowly over time after beingimplanted. As such, the biodegradability of the plate can cause uniformdegradation so as to avoid substantial shortening and/or shrinking ofthe dimensions of the plate. It is thought, without being bound totheory, that the biodegradability arises from water or other body fluidpermeating into the implanted plate so as to soften the polymers andrelax the orientation. Also, the designed polymer molecule orientationcan aid in providing the biodegradability that does not result in theshorting and/or shrinking For example, the biodegradable plate candegrade so that about 75% of the initial mass has degraded after about10 months, more preferably after about 6 months, and most preferablyafter about 4 months. This can also result in the plate fully degradingin about 14 months, more preferably about 1 year, and most preferably inabout 10 months. Accordingly, the implantable plate can be configured tobiodegrade so that the bone supports more weight in comparison to theimplantable plate in less than 12 weeks, more preferably in less than 8weeks, even more preferably less than 4 weeks, and most preferably after2 weeks.

Also, the implantable plates can be configured to have a desired amountof polymer orientation that allows the plate to be bent up to an angleof about 45 degrees, or more if desired. In one embodiment, the platecan be configured to be bent to an angle up to or about 90 degreeswithout heat. In another embodiment, the plate can be configured to bebent without heat to an angle less than or about 45 degrees, or lessthan or about 35 degrees. In another configuration, the plate can bebent without heat to an angle less than or about 30 degrees.Alternatively, it can be preferred to have a more rigid plate that onlybends up to or about 25 degrees, less than about 20 degrees, or lessthan about 15 degrees. In any event, the foregoing bendability can beachieved in the polymeric plates without the aid of any heat. That is,the plates can be bent without heating any portion of the plate and notcausing any breakage such as fractures, cracks, deformations, or otherstructurally catastrophic malformations.

Furthermore, in order to achieve the bendability without any thermalenergy, the polymer molecules can be oriented within the implantableplate to have a desired amount of orientation in substantially onedirection. As used herein, the term “one direction” is meant to includepolymers aligned in substantially one direction, but not necessarilyentirely in only one direction. For example, when the polymer isbiodegradable, such orientation includes less than about 40% of thepolymer molecules oriented in substantially one direction. In anotherconfiguration, about 10% to about 30% or the polymer molecules can beoriented in substantially one direction, or about 15% to 25% oriented insubstantially one direction.

In one embodiment, it can be preferred to prepare the implantable platewith a biodegradable polymer and another material such as an inertpolymer, natural polymer, magnesium fiber, and/or silicon fiber. In oneaspect, this can be beneficial to allow biodegradability over time andstill retain some structural support after the degradable portion hasbeen depleted. As such, this can be favorable for complex bonereconstructions that may need some long-term support. That is, aninitially high amount of support can be provided that decreases overtime until a final amount of support is obtained, which allows the boneto reform and strengthen as the biodegradable portion is depleted.Alternatively, additional biodegradable materials can enhance thebiodegradability of the implantable plate. For example, thebiodegradable polymer to other material ratio can range from about 10 toabout 1, from about 8 to about 4 in other configurations, from about 6to about 4 in yet other configurations, and vice versa depending on thecharacteristic desired

Moreover, an embodiment of the implantable plate can be configured tominimally shrink in a water bath maintained at about 37° C. As such, theplate can be configured to have a dimension, such as length or widththat shrinks less than about 6% of its original dimension in a period of10 days, less than about 4% in other configurations, and less than 3% instill other configurations.

IX. Manufacturing Polymeric Plates

In one embodiment of the present invention, a method of manufacturingcan produce an implantable plate having the features described inaccordance with the present invention. Such a method of manufacturingcan employ the foregoing compositions, equipment, systems, and processesas previously described. An exemplary method of manufacturing isdescribed in more detail below.

FIG. 8 illustrates an embodiment of an implantable plate fabricationmethod 400. Such a plate fabrication method 400 can include and utilizeany of the various equipment, components, and processes described inconnection to FIG. 1 through FIG. 7. Accordingly, the plate fabricationmethod 400 includes preparing a polymer to have the thermoplasticcharacteristics and resulting plate strength and flexibility profiles asdescribed above (402). By preparing the polymer composition to have theproper components and concentrations, the implantable plate can beprepared to have the preferred structural and flexibility features.

In one embodiment, the polymer composition can be extruded (404).Extruding the polymer composition can be beneficial in order to providethe proper configuration, consistency, temperature, and the like beforeinjection molding. This can include further mixing and/or compaction ofthe polymeric materials as well as heating the polymer past itssoftening point, melting point, and/or glass transition temperature.

In any event, the polymer can be supplied into a polymer pre-mold (406).Within the pre-mold, the polymer composition can be pressurized so as tohave the proper pressure for being injected into the injection mold(408). Additionally, the polymer composition can be dried in thepre-mold to remove any moisture (410).

After being properly conditioned, the polymer composition can beintroduced into an injection mold for injection molding (412).Additionally, the polymer molecules in the composition can be orientedby a gate to have a desired amount of orientation (414). The injectionmolded body can then be moved into a post-mold (416). While in thepost-mold, the molded body can be cooled for further processing (418).

Accordingly, after being substantially cooled and solidified, the platefabrication method 400 can include drilling the fastener holes (420).Optionally, after fastener holes have been drilled into the moldedarticle, the fastener holes can be tapped in order to have the properthreading in order to cooperate with any threaded bolt or screw used asa fastening means (422). Various known methods of using taps in order toform threaded holes can be used in connection therewith.

In one embodiment, either before or after the holes have been formed,the implantable plate can be separated from the polymeric runners orother polymeric features (424). More specifically, when the molded bodyis formed, which typically includes molded runners, vents, dividers,cold wells, and plate regions, the plate region can be separated for theother features. In any event, the separation can be performed bycutting, pressing, stamping, or otherwise removing the polymer featuresfrom the plates.

Moreover, after the plate has been separated from other polymericfeatures and drilled to provide fastener holes, the plate can befinished (426). Finishing can include grinding, surfacing, sanding orotherwise removing anomalies or other surface features on the moldedplate. Also, the finishing can include providing a coating to the moldedplate. Additionally, any other well-known process for finishing a moldedarticle can be used in connection herewith in order to substantiallyfinish the plate into a useable and implantable condition. Also,additional finishing may not be necessary because injection molding canprepare an implantable plate that is ready for use in a surgicalprocedure.

While certain features and embodiments of the present invention havebeen described, the present invention may be embodied in other specificforms without departing from its spirit or essential characteristics.The described embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

1. A method of manufacturing an implantable plate for providing supportto a bone of a subject when affixed thereto, the method comprising:providing a molten, semi-crystalline biocompatible polymeric compositionthat includes a plurality of polymeric molecules; exposing the molten,semi-crystalline biocompatible polymeric composition to a shear stressso as to align at least a portion of the polymeric molecules insubstantially a polymer flow direction; injection molding the molten,semi-crystalline biocompatible polymeric composition in an injectionmold cavity so as to form a polymeric body, wherein at least a portionof the polymeric body is configured to have a shape of an implantableplate at least partially defined by a top surface and bottom surface;removing the polymeric body from the injection mold; and forming atleast one fastener hole within the implantable plate portion after beingremoved from the injection mold, wherein the at least one fastener holeextends from the top surface to the bottom surface.
 2. The method as inclaim 1, wherein the forming the at least one fastener hole includesdrilling holes in the implantable plate portion.
 3. The method as inclaim 1, wherein the shear stress includes passing the molten,semi-crystalline polymeric composition through a gate that is configuredfor orienting the polymeric molecules in substantially the polymer flowdirection.
 4. The method as in claim 3, achieving the predeterminedamount of polymeric molecule orientation in substantially the polymerflow direction further comprising: configuring the injection mold tohave at least one of a runner, a runner network, a flow divider, a coldwell, a gate region, mold cavity orientation, vents, or moldtemperature; and manipulating at least one of the runner, the runnernetwork, the flow divider, the cold well, the gate, the gate region,mold cavity orientation, the vent, mold temperature, polymercomposition, and polymer flow rate so as to achieve the predeterminedamount of polymeric molecule orientation.
 5. The method as in claim 3,further comprising configuring the gate to have at least one aperturethat imparts the shear stress to the molten, semi-crystalline polymericcomposition passing through the gate, wherein the at least one apertureis pre-designed to achieve a predetermined amount of polymeric moleculeorientation in substantially the polymer flow direction.
 6. The methodas in claim 5, wherein the at least one aperture has a cross-sectionallength from about 10% to about 60% of at least one of an averagecross-sectional length of the cavity or a cross-sectional length of arunner.
 7. The method as in claim 1, wherein the implantable plate iscapable of being bent without heat to an angle of less than or about 90degrees.
 8. The method as in claim 7, wherein the implantable plate iscapable of being bent without heat to an angle of less than or about 30degrees.
 9. The method as in claim 1, wherein the implantable plateshrinks less than about 6% of an original dimension when maintained in afluid at 37° C. for 10 days.
 10. The method as in claim 1, furthercomprising configuring the implantable plate to be biodegradable withina medium maintained at 37° C.
 11. The method as in claim 1, furthercomprising configuring the implantable plate to biodegrade so that thebone supports more weight in comparison to the implantable plate after 6weeks.
 12. The method as in claim 1, wherein the predetermined amount ofpolymer molecule orientation includes more than about 10% and less thanabout 40% of the polymer molecules being oriented in substantially thepolymer flow direction.
 13. The method as in claim 1, further comprisingconfiguring the injection molding to use a mold having a cavity that issubstantially devoid of any pins or protrusions extending through thecavity so as to result in an implantable plate substantially devoid ofjoint lines.
 14. The method as in claim 1, further comprisingintroducing fibers into the injection mold during the injection moldingprocess so as to be encapsulated within the polymeric body, the fibersbeing selected from the group consisting of magnesium fiber,micro-porous silicon fiber, nano-porous silicon fiber, organic fiber,ceramic fiber, and combinations thereof.
 15. The method as in claim 1,further comprising configuring a portion of the plate to be capable ofdelivering a drug after being implanted.
 16. The method as in claim 15,wherein the portion is a polymeric coating on the plate.
 17. The methodas in claim 1, further comprising at least one of the following: mixingthe polymeric composition in a mixer; extruding the polymericcomposition as a thermoplastic extrudate; heating the polymericcomposition before being introduced into the injection mold introducingthe polymeric composition into the injection mold under pressure;cooling the polymeric body after being removed from the injection mold;drilling a fastener hole with at least one of a drill bit or a laser;forming threads in a wall that defines the at least one fastener hole;separating the implantable plate portion form the polymeric body;finishing the implantable plate portion into an biocompatibleimplantable plate; or configuring the implantable plate to bebiodegradable.
 18. A method of manufacturing an implantable plate forproviding support to a bone of a subject when affixed thereto, themethod comprising: providing a molten, non-crystalline biocompatiblepolymeric composition that includes a plurality of polymeric molecules;exposing the molten, non-crystalline biocompatible polymeric compositionto a shear stress so as to align at least a portion of the polymericmolecules in substantially a polymer flow direction; injection moldingthe molten, non-crystalline biocompatible polymeric composition in aninjection mold cavity so as to form a polymeric body, wherein at least aportion of the polymeric body is configured to have a shape of animplantable plate at least partially defined by a top surface and bottomsurface; removing the polymeric body from the injection mold; andforming at least one fastener hole within the implantable plate portionafter being removed from the injection mold, wherein the at least onefastener hole extends from the top surface to the bottom surface. 19.The method as in claim 18, wherein the shear stress includes passing themolten, non-crystalline polymeric composition through a gate that isconfigured for orienting the polymeric molecules in substantially thepolymer flow direction.
 20. The method as in claim 19, achieving thepredetermined amount of polymeric molecule orientation in substantiallythe polymer flow direction further comprising: configuring the injectionmold to have at least one of a runner, a runner network, a flow divider,a cold well, a gate region, mold cavity orientation, vents, or moldtemperature; and manipulating at least one of the runner, the runnernetwork, the flow divider, the cold well, the gate, the gate region,mold cavity orientation, the vent, mold temperature, polymercomposition, and polymer flow rate so as to achieve the predeterminedamount of polymeric molecule orientation.